(Reuters) – Standard Poors on Wednesday said Facebook Inc will join its SP 500 stock index after the close of trading on December 20, cementing the social media networks rise into one of the biggest, most powerful U.S. companies. The decision follows Facebook reporting its fourth straight profitable quarter in October, one of the criteria that SP uses to determine eligibility for the index. Facebook shares rose 4.3 percent to $51.51 following SPs announcement after regular market hours. SP said on December 20 it will also add marketing solutions company Alliance Data Systems Inc and floor covering company Mohawk Industries Inc to the SP 500, and remove Abercrombie Fitch Co, JDS Uniphase Corp and Teradyne Inc. Facebook will also replace Williams Cos in the SP 100 index of large U.S. companies.